Are adjustable punch balls any good? What are their advantages and disadvantages?

I was going to get a heavy bag but theres nowhere to put it and the frames are too expensive. Are punchballs any good?





http://www.google.co.uk/imgres?imgurl=ht鈥?/a>|||Yes, punching someone in the balls makes it very hard for them to adjust and pretty much sucks everything out of them....





Just as Zab Judah in the Cotto fight....